Light-Tunable Charge Density Wave Orders in MoTe_{2} and WTe_{2} Single Layers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Group VI monolayer transition metal ditellurides are promising materials for electronic applications.
• Understanding and controlling charge order phenomena is crucial for novel device functionalities.
• Existing methods for stabilizing charge density waves are limited, especially in insulating 2D materials.

Purpose of the Study:

• To investigate the potential of ultrafast optical pumping to unveil and stabilize hidden charge orders.
• To characterize the properties of light-induced transient charge ordered phases in 2D transition metal ditellurides.
• To provide experimental fingerprints for identifying these transient phases.

Main Methods:

• Constrained density functional theory (DFT) modeling was employed to simulate the effects of optical pumping.
• Analysis focused on insulating 2H and semimetallic 1T^{'} phases of group VI monolayer transition metal ditellurides.
• Calculations identified critical laser fluences and predicted optical and Raman spectroscopy signatures.

Main Results:

• Ultrafast optical pumping induces multiple transient charge density wave (CDW) orders in insulating 2H phases.
• These transient CDWs exhibit light-tunable distortion, periodicity, electronic structure, and band gap.
• Semimetallic 1T^{'} phases transform into a transient metallic phase with a 2D diamond cluster structure upon optical pumping.

Conclusions:

• Ultrafast optical pumping is a viable method to stabilize elusive charge density waves in 2D transition metal dichalcogenides.
• This technique allows for dynamic control over the properties of induced charge ordered states.
• The identified optical and Raman fingerprints will guide experimental validation using ultrafast pump-probe spectroscopy.